Role of D-GADD45 in JNK-Dependent Apoptosis and Regeneration in Drosophila

The GADD45 proteins are induced in response to stress and have been implicated in the regulation of several cellular functions, including DNA repair, cell cycle control, senescence, and apoptosis. In this study, we investigate the role of D-GADD45 during Drosophila development and regeneration of the wing imaginal discs. We find that higher expression of D-GADD45 results in JNK-dependent apoptosis, while its temporary expression does not have harmful effects. Moreover, D-GADD45 is required for proper regeneration of wing imaginal discs. Our findings demonstrate that a tight regulation of D-GADD45 levels is required for its correct function both, in development and during the stress response after cell death

Development and regeneration of Drosophila wing imaginal discs: the role of IncRNAs and the stress sensor D-GADD45

[eng] Long non-coding RNAs (lncRNAs) are defined as transcripts longer than 200 nucleotides that lack protein-coding potential. Although multiple examples of functional lncRNAs have been described, particularly regulating gene expression at different levels, the function of the vast majority of them remains to be elucidated. Here, we use the Drosophila wing imaginal discs as a model system to study the involvement of lncRNAs in development and regeneration. Additionally, we also studied the role of the stress sensor protein Drosophila Growth Arrest and DNA Damage 45 (D-GADD45) in the wing disc. For the study of lncRNAs, we used transcriptomic data from developing and regenerating wing discs. We identified a set of ~200 lncRNAs expressed in development, as well as 131 differentially-expressed (DE) lncRNAs in regeneration. Among them, we focused on the study of lncRNAs CR40469 and CR34335, which share 99.1% sequence identity, however, their expression pattern is far from similar: while CR40469 is upregulated in regeneration, the expression of CR34335 is inhibited upon damage. We generated a CR40469 knock-out mutant, for which no phenotypes were detected in normal conditions. Nevertheless, upon the induction of cell death, these mutants lost their regeneration capacity, suggesting a putative function of CR40469 in regeneration. Moreover, we characterised the molecular changes occurring in the mutant, revealing a set of 95 DE genes compared to controls. On the other hand, no phenotypes were detected for CR34335 mutants, neither in development nor in regeneration, suggesting that this lncRNA is dispensable for both processes. Regarding the study of D-GADD45, we activated its expression ectopically in the wing discs, resulting in increased apoptosis. Through genetic interaction experiments, we described the D-GADD45-induced cell death as dependent on the activation of the JNK signalling pathway. Additionally, we described a JNK-independent decrease in cell proliferation upon sustained activation of D-GADD45. Finally, we identified D-GADD45 as an essential gene for the regeneration of wing discs, as the use of RNAi constructs against D-GADD45 severely impairs the recovery process after the induction of cell death

Role of <i>D-GADD45</i> in JNK-Dependent Apoptosis and Regeneration in <i>Drosophila</i>

The GADD45 proteins are induced in response to stress and have been implicated in the regulation of several cellular functions, including DNA repair, cell cycle control, senescence, and apoptosis. In this study, we investigate the role of D-GADD45 during Drosophila development and regeneration of the wing imaginal discs. We find that higher expression of D-GADD45 results in JNK-dependent apoptosis, while its temporary expression does not have harmful effects. Moreover, D-GADD45 is required for proper regeneration of wing imaginal discs. Our findings demonstrate that a tight regulation of D-GADD45 levels is required for its correct function both, in development and during the stress response after cell death

Genomic and functional conservation of lncRNAs: lessons from flies

Over the last decade, the increasing interest in long non-coding RNAs (lncRNAs) has led to the discovery of these transcripts in multiple organisms. LncRNAs tend to be specifically, and often lowly, expressed in certain tissues, cell types and biological contexts. Although lncRNAs participate in the regulation of a wide variety of biological processes, including development and disease, most of their functions and mechanisms of action remain unknown. Poor conservation of the DNA sequences encoding for these transcripts makes the identification of lncRNAs orthologues among different species very challenging, especially between evolutionarily distant species such as flies and humans or mice. However, the functions of lncRNAs are unexpectedly preserved among different species supporting the idea that conservation occurs beyond DNA sequences and reinforcing the potential of characterising lncRNAs in animal models. In this review, we describe the features and roles of lncRNAs in the fruit fly Drosophila melanogaster, focusing on genomic and functional comparisons with human and mouse lncRNAs. We also discuss the current state of advances and limitations in the study of lncRNA conservation and future perspectives

Chromatin organization and function in Drosophila

Eukaryotic genomes are packaged into high-order chromatin structures organized in discrete territories inside the cell nucleus, which is surrounded by the nuclear envelope acting as a barrier. This chromatin organization is complex and dynamic and, thus, determining the spatial and temporal distribution and folding of chromosomes within the nucleus is critical for understanding the role of chromatin topology in genome function. Primarily focusing on the regulation of gene expression, we review here how the genome of Drosophila melanogaster is organized into the cell nucleus, from small scale histone-DNA interactions to chromosome and lamina interactions in the nuclear space